1. Field of the Invention
The present invention relates to a watertight electric connector, and more particularly to watertight electric connectors for use in an electric circuit of a machine or a vehicle to be used outdoors.
2. Description of the Related Art
In an environment where there is a possibility of exposure to rainwater or the like, a watertight electric connector is used to join wire harnesses or a wire harness and an electrical device since short circuit due to intrusion of water, contact failure resulting from oxidation of the surface of a splicing fitting with the passage of time due to moisture, and so on are unallowable from standpoints of electric control and safety management.
Such a watertight electric connector is disclosed in, for example, U.S. Pat. No. 4,820,181. FIG. 6 illustrates the watertight electric connector.
The connector has a watertight packing inserted in the joint between male and female connector housings a and b. Although terminal members are built in the housings a and b, since they have no relation to the watertight structure of the connector, the internal structure of the connector is not illustrated.
In the watertight electric connector, a ring-shaped packing c is set on a mating outer wall a.sub.1 of the male connector housing a so as to complete a watertight joint between the outer wall a.sub.1 and an inner engaging surface b.sub.1 of a columnar portion of the female connector housing b. If the outer surface of the packing c is exposed, scrapes are physically formed on the outer surface by rubbing during connection of electric wires to a wire harness, and transportation, storage and attachment of the connector subsequent to the connection, so that the watertight effect of the packing c is hindered by the scrapes. In order to solve the above problem, a fixed protection wall a.sub.2 is extended from the outer face of the male connector housing a, thereby bringing some effects. However, the necessity of a cavity a.sub.3 into which the female connector housing b is inserted leads to the following disadvantages:
First, since the protection wall a.sub.2 (outside diameter D.sub.1) is disposed outside a columnar portion b.sub.2 (outside diameter D.sub.2), the dimension of the connector is larger by D.sub.1 -D.sub.2 =d than that of a connector without the protection wall a.sub.2. In order to save the mounting space for a connector in a machine or a vehicle, it has been recently requested that the maximum outside dimension be made as small as possible. In particular, a multiway connector has been strongly required to be small in outside dimension.
Furthermore, when the above protection wall a.sub.2 is used, it is likely that dust floating in the air will intrude into the cavity a.sub.3, stick to the surface of the packing c, and form minute scrapes on the surface of the packing c due to the slide on the columnar portion inner engaging surface b.sub.1 when the connector housings a and b are mated with each other. The scraping is one of causes of intrusion of moisture into the connector. Incorrect operations of an electric control circuit in a machine or a vehicle cannot be absolutely permitted in relation to electronicization and complication thereof. However, some trouble, such as contact failure at an electric joint and increase in electric resistance, still arises due to the intrusion of moisture, and thus the request for a watertight electric connector having improved watertight performance has been increased.